1. Field of Use
The present invention relates to multicomputer systems and more particularly, to closely coupled multicomputer systems.
2. Prior Art
It is well known to interconnect several independently operated computer systems together for processing jobs. In one well known type of arrangement, a master computer system is connected to transfer programs and data to higher speed slave systems through a high speed peripheral device such as a disk for execution. A scheduling program being executed by the master system determines which programs should be activated on which slave system. This type of system has been characterized as a a loosely coupled system because of the physical separation of the computer systems, message-oriented interprocessor communication and independent operating systems.
In other types of loosely coupled systems, certain resources are defined as global meaning that they are accessible from all parts of the system as if they were located on the system on which the user is located. In this type of system, it is necessary to provide for sessions during which a user of one system can utilize a resource attached to another system. This makes it necessary to provide for synchronizing the use of these resources so that access is provided to the most current version at any given instant of time. Also, there is a limitation as to the number of sessions which can take place simultaneously. An example of this type of system is disclosed in U.S. Pat. No. 4,851,988.
Another type of multicomputer system termed a closely coupled distributed system includes a number of separate processors and memories connected by a message oriented computer interconnect organized as a star coupler having radial ports to which the processors connect. Each port is responsible for arbitration, path selection and data transmission. In this system, although the files can be shared, the file management facilities are unaware of whether they are executing in a clustered environment. Therefore, additional means in the form of a distributed lock manager is provided for synchronizing cluster file activity. This increases overhead and inter-node traffic in determining when a requested resource can be accessed. The result is increased system complexity. This system is described in an article titled, "VAXclusters: A Closely-Coupled Distributed System," published in ACM Transactions on Computer Systems, Vol. 4, No., May 1986.
Accordingly, it is a primary object of the present invention to provide a closely-coupled system which maximizes the use of available operating system facilities.
It is further object of the present invention to provide a closely-coupled system which requires no changes to be made in the applications being run on the system.